1. Field of the Invention
The invention relates to turbochargers, and is particularly concerned with problems associated with what is known as attitude setting of turbochargers.
2. Description of the Related Art
A turbocharger basically comprises a compressor and a turbine coupled together, generally with a common shaft. Engine exhaust gases are fed into the turbine and rotate the turbine and the common shaft. This drives the compressor, which is used to force air into the engine.
The compressor has an inlet and an outlet, as does the turbine. On any given engine, there may be an optimum position for the location of the compressor inlet and/or outlet and an optimum position for the location of the turbine inlet and/or outlet. The compressor position may not necessarily have the same attitude with respect to the turbine position on different engines.
It has therefore been necessary to provide means for clamping the compressor housing to the turbine housing in different positions so that the attitude of the compressor housing with respect to the turbine housing can be adjusted to suit any given engine.
This not only necessitates the use of complicated clamping rings and associated seals, but a very sophisticated jig is necessary to hold and adjust the housings prior to clamping them together.
A further problem associated with known turbochargers is that extensive milling and drilling is required to manufacture the housings.
We have now developed a method of turbocharger manufacture, which eliminates or substantially reduces the above-mentioned problems.
According to the invention, a method of manufacturing a turbocharger comprises designing a turbocharger housing having a compressor housing portion, a turbine housing portion, and a connecting portion, the geometry of at least the connecting portion being circular and concentric with respect to a common centerline passing through all three positions, and then manufacturing the housing using a casting technique, the attitude of the compressor portion with respect to the turbine portion being preselected prior to casting by appropriate adjustment of the mould utilized in the casting process.
There may, for example, be a compressor housing mould portion and a turbine housing mould portion, the two mould portions being rotatable with respect to one another about the said centerline before casting takes place.
It is preferred that each inlet and outlet to the housing is circular, with an annular groove, so that connections to other components can be made using annular seals and clamping rings, such as those known as MARMAN fittings.
Preferably the dimensions of each inlet and outlet are made substantially identical, so that a single size of clamping fitting can be used for connection to other components.
The invention includes a turbocharger having a housing manufactured by the method according to the invention.
There may be a series of different turbochargers having different attitude settings.
The invention includes casting apparatus for use in carrying out the method according to the invention.
The apparatus preferably has a compressor housing mould portion and a turbine housing mould portion, the two mould portions being rotatable with respect to one another.